Electrochemical assessment on the corrosion risk of steel embedment in OPC concrete depending on the corrosion detection techniques

Abstract

This study examines the corrosion of embedded steels in concrete or mortar using galvanic cell, half-cell, polarisation technique and mass loss method. The chloride content in the cast ranged between 0.0 and 3.0% by weight of cement. After 28 days of curing, the specimens were subjected to wet/dry cycles for 15 weeks. It was found that the values obtained from the galvanic current and half-cell potential provided clear indication of whether corrosion started or not, while they gave no informative data on the corrosion propagation. For the polarisation technique, an increase in the chloride content resulted in increased corrosion rate and it was possible to monitor the development of corrosion. The chloride threshold level for visible, weighable pitting corrosion was obtained by the mass loss method, accounting for about 0.79% by weight of cement. This value was adopted to calculate the values at visible rusting on the steel surface for each technique, accounting for 0.63 mA m(-2), -343 mV vs. SCE, 9.94 and 8.29 mA m(-2) for galvanic current, half-cell potential, corrosion rate of linear polarisation and Tafel extrapolation, respectively. (C) 2008 Elsevier B.V. All rights reserved.